<div class="main">
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
  <div class="card"></div>
</div>

<style>
/* From Uiverse.io by Praashoo7  - Tags: arrow, transition, cool checkbox, loader, arrow */
.main {
  display: flex;
  flex-wrap: wrap;
  width: 15em;
  align-items: center;
  justify-content: center;
}

.card {
  width: 40px;
  height: 40px;
  border-top-left-radius: 10px;
  background: lightgrey;
  transition: 0.4s ease-in-out, 0.2s background-color;
  background: rgba(255, 255, 255, 0.2);
  backdrop-filter: blur(5px);
  margin: 0.2em;
  border-radius: 5px;
  box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.3);
  animation: 2s loading90 infinite;
}

.card:nth-child(2) {
  animation-delay: 1s;
}

.card:nth-child(4) {
  animation-delay: 1s;
}

.card:nth-child(6) {
  animation-delay: 1s;
}

.card:nth-child(8) {
  animation-delay: 1s;
}

.card:nth-child(10) {
  animation-delay: 1s;
}

.card:nth-child(12) {
  animation-delay: 1s;
}

.card:nth-child(14) {
  animation-delay: 1s;
}

@keyframes loading90 {
  0% {
    background: rgba(255, 255, 255, 0.2);
  }

  50% {
    background: limegreen;
  }

  100% {
    background: rgba(255, 255, 255, 0.2);
  }
}

</style>
    